Calcium-vanadium ferrimagnetic garnets

ABSTRACT

Provided are magnetic materials suitable for use in microwave circuit elements and having excellent properties such as a very low value of the ferromagnetic resonance linewidth, high curie temperature, a suitably controllable value of the saturation magnetization and improved temperature stability of the saturation magnetization. Such materials are obtained by substituting Ca ions located on the 24c site and Fe ions on the 16a site in calcium-vanadium garnets with Y ions and Sn ions, respectively, or by further substituting the ions located on the 24d site in the calcium-vanadium garnets thus modified with Ge ions.

Takamizawa et al.

[ 1 Oct. 2, 1973 I CALClUM-VANADIUM FERRIMAGNETIC GARNETS [75]Inventors: Hideo Takamizawa; Keiichi Yotsuyanagi, both of Tokyo, Japan[73] Assignee: Nippon Electric Company, Limited,

Minato-ku, Tokyo, Japan [22] Filed: Apr. 1, 1971 [21] Appl. No.: 130,343

[30] Foreign Application Priority Data Apr. 3, 1970 Japan 45/28948 JulyI, 1970 Japan 45/57966 [56] References Cited UNITED STATES PATENTSBuhrer Geller Geller 252/6257 X Takamizawa et al. 252/6257 11/1964Geller 252/6259 X 6/1969 Remeika et al 350/1 OTHER PUBLICATIONS Gelleret al., Journal of Applied Physics, Vol. 35, No. 3, pp. 570-572, March1964.

Yudin et al. Physics Letters, Vol. 28A, No. 7, PP. 483-484, January,1969. 0

Primary Examiner-Oscar R. Vertiz Assistant Examiner-J. CooperAttorney-Sandoe, Hopgood & Calimafde [57] ABSTRACT Provided are magneticmaterials suitable for use in microwave circuit elements and havingexcellent properties such as a very low value of the ferromagneticresonance linewidth, high curie temperature, a suitably controllablevalue of the saturation magnetization and improved temperature stabilityof the saturation magnetization. Such materials are obtained bysubstituting Ca ions located on the 24c site and Fe ions on the 16a sitein calcium-vanadium garnets with Y ions and Sn ions, respectively, or byfurther substituting the ions located on the 24d site in thecalcium-vanadium garnets thus modified with Ge ions.

2 Claims, 9 Drawing Figures PATENTED 21975 3,763,045 SHEET 3 or 4INVENTORS HIDEO TAKAMIZAWA KEHCHI YOTSUYANAGI iii, 4%

ATTORNEYS CALCIUM-VANADIUM FERRIMAGNETIC GARNETS BACKGROUND OF THEINVENTION Field of the Invention The present invention relates tocalcium-vanadium (Ca-V) ferrimagnetic garnets for use in microwavecircuit elements operating in the VHF, UHF or SHF band range. Among therequired characteristics of magnetic materials for use in such microwavecircuit elements are low magnetic losses and small temperaturevariations of the saturation magnetization values (4 11' Ms). Desiredvalues of 4 11- Ms will vary according to the application of themagnetic materials. The essential condition for reducing the magneticloss is that the ferromagnetic resonance linewidth (AI-I) be as low aspossible. It has been known that the higher the Curie temperature, thelower becomes temperature variation of the saturation magnetization (41r Ms) and that in order to lower the value of the linewidth (AH), whichis subject to change with the sintering density and the presence orabsence of a second phase, the sintering densities must be madesufficiently large and there should be no second phase formation.

Description of the prior art The yttrium-iron garnets (YIG) that havebeen most commonly used as magnetic materials in microwave applicationsoffer the advantages of lower 4 7r Ms values, higher Curie temperaturesand lower magnetic losses than conventional spinel-type ferrites such asnickel series ferrites or magnesium-manganese series ferrites. Theseadvantages of the yttrium-iron series garnets are considerably offset bydetects such as the necessity for the use of yttrium oxide which is anexpensive raw materials and the need for sintering at extremely hightemperatures and for long time intervals which are not suited forlarge-scale industrial production.

It has been proposed to substitute part of yttriumiron garnets with A1for lowering the saturation magnetization. See Physical Review, vol.110, 1958, p. 73. Such garnets have another defect of a rapid decreasein the Curie temperature which inevitably causes a large variation of 41r Ms with a temperature variation.

The unmodified Ca-V garnet is known for featuring high Curietemperatures in spite of low 4 1r Ms, but its high A H renderedpractical application extremely difficult.

It has been also proposed to substitute part of the Ca-V garnet withyttrium and indium oxides in order to decrease A H. See MaterialResearch Bulletin, vol. 4, 1969, p. 825 838. However, such substitutioncauses decrease in Curie temperature and increase in 41: Ms.

It is, therefore, the object of the invention to provide improvedmicrowave circuit element materials for use in the VHF, UHF or SHF bandrange, having excellent characteristics such as low ferromagnetic.resonance linewidth values and high Curie temperatures.

The garnet compositions are generally expressed by a normal formula unit(A (B (C90 where the first, second and third parentheses representrespectively the 240, 16a and 24d sites and A, B and C denote atomsoccupying the respective sites. Fe has a preference for the twodifferent sub-lattice sites (the 16a and the 24d sites) and the Fe-Fesuper-exchangeinteractions in each of and between these sub-lattic sitescause the Fe magnetic moments at the 16a and 24d sites to be coupledanti-ferromagnetically. Under the situation of the relative siteunbalance, wherein the magnetic moment at the 24d site is not equal tothat at the 16a site, the garnet compositions manifest ferrimagnetism.It has been generally considered that the compositions manifestanti-ferromagnetism in case of the site balance and at which an abnormalphenomenon of A H occurs.

The value of 4 7r Ms is determined by the relative site unbalance in themagnetic moment between the 16a and 24d sites for which Fe has a strongpreference, while the temperature variation of4 11- Ms changes with thenumbers of iron ions located on each sub-lattice site, kinds ofnon-magnetic ions replacing the iron ions, and kinds of ions located onthe 24c site.

The unmodified calcium-vanadium garnet can be expressed by a normalformula unit (Ca (Fe (Fe 1.5 1.5) 12- SUMMARY OF THE INVENTION Accordingto the invention, calcium-vanadium garnets are improved by substitutingCa ions on the 240 site and Fe ions on the 16a site with Y ions and Snions, respectively, or by further substituting ions on the 24d site inthe thus-modified garnets with Ge ions. The improved calcium-vanadiumgarnets are featured by sufficiently low A H values, high Curietemperatures, 41rMs values within controllable suitable ranges, smalltemperature variations in the value of 4wMs and low manufacturing costs.

The calcium-vanadium garnet compositions substituted with Y and Sn ofthis invention are expressed by the chemical formula:

in which the values of x and y are required to satisfy the followingrelations:

0 y 2.5 Where the difference between numbers of Fe ions located on the16a site and the 240! site is 0.1 or less, an abnormal phenomenon of A His observed and the values of A H cannot be improved. Of course,ferrimagnetism disappears if the difference is. zero. Thus, the range of|(2x) 1.5 +0.5x +0.5y)| 0.1 ,i.e. 0.8 2 3x +y 1.2, should be excludedfrom the above-men tioned Y-and Sn-substituted Ca-V garnet composins otnvention.

It is preferable that the values of x and y are within the ranges of 0.3x 0.5 and 1.2 y g 2.0, respectively. With such compositions, the valueof A H is less than 10 oersteds.

According to this invention, the Y-and Sn-substituted Ca-V garnets canbe further substituted with Ge. The garnet compositions thus obtainedcan be expressed as in which at, y and 2 should be within the ranges of0 x E 0.5, 1.0 g y 2.4 andO z 0.5,respectively and they should satisfythe relation of 1.5 0.5x 0.5y 0.5z 0. Where the difference of thenumbers of Fe ions between 16a and 24d sites I (2 x) (1.5 0.5x

+ 0.5y 0.5z)| is 0.1 or less, the abnormal phenomenon of A H isobserved, as mentioned previously. Accordingly, the compositionssatisfying the relation of 0.8 I 3x y z 1.2 should be excluded. It ispreferable that x, y and 2 lie within the ranges of 0.25 x 0.5, 1.2 y2.4 and 0.2 1 0.4, respectively. The Y-, Snand Gesubstituted Ca-Vgarnets within such ranges have low A H of less than 20 oersteds.

BRIEF DESCRIPTION OF THE DRAWING FIGS. 1, 2 and 3 show, respectively,ferromagnetic resonance linewidths (A H), Curie temperatures and 4 1rMsas a function of x for the Y- and Sn-Substituted Ca-V ferrimagneticgarnets of this invention with the compositions expressed by the formulamentioned above;

FIG. 4 is a diagram illustrating the effective range of the values of xand y in the Y- and Sn-substituted Ca-V garnet compositions expressed asabove;

FIG. 5 shows the effect of x on 4 qrMS and A H for the Y-, SnandGe-substituted Ca-V garnet composition expressed by the mentionedformula where y 1.4 and z 0.3;

FIGS. 6 and 7 show the effect of y on A H and Curie temperature,respectively for the Y- and Sn-substituted Ca-V garnets;

FIG. 8 shows influence of z(Ge) on A H and 41rMs for the Y-, SnandGe-substituted Ca-V garnet compositions expressed by the formulamentioned above; and

FIG. 9 is a graph of the 41rMs versus temperature characteristics ofgarnet compositions of the prior art and of this invention whichillustrates the advantages of this invention.

DETAILED DESCRIPTION Samples mentioned below were prepared by theemethod well known in the art. In detail, starting materials CaCO Fe V 0Sn0 6e0 and Y 0 in such amounts were weighed, 350 grams in total in eachcase, so that each of the compositions shown in Tables may be finallyobtained. These materials were admixed in a ball mill made of steel,presintered at 900 C for 4 hours, compressed into the desired shapes,and then sintered at a temperature of 1210 C to 1300 C for 10 hours inair. The sintered products were removed from the furnace when thefurnace temperature cooled down to 300 C. Then the values of thesaturation magnetization (41rMs) at room temperature (23 25 C), thelinewidth (A H) at 9.5 GHz, and the Curie temperature were measured.

Table 1 lists the results of measurements for the unsubstituted,Ge-substituted, Sn-substituted, Snand Gesubstituted, Y- andSnsubstituted and Y-, Snand Gesubstituted Ca-V garnet compositions todemonstrate the successively promoted substitution effects, as regards adecrease in the linewidth A H and an increase in the Curie temperature.Sample No. l, or unmodified Ca-V garnet has low 4 rrMs and high Curietemperature, but A H is as high as 370 (i.e., large magnetic loss).Therefore, practical use of this garnet is substantially impossible. Itwill be noted with No. 2 sample in which a fraction of Fe ion on the 24dsite is replaced with Ge, that the Ge-substitution has contributed to areduction in A H 110), or less than one-third of that for the unmodifiedCa-V garnet. The effectiveness of Sn-substitution, or the substitutionof Sn for a fraction of Fe ion on the 16a site of the unmodified Ca-Vgarnet compositions as indicated in sample Nos. 3 and 4, for reductionin both 41rMs and A H will also be appreciated. The A H value of bout190 has become almost one-half of that for the unmodified Ca-V garnetcomposition. A comparison of No. 3 and No. samples, however, indicatesthat the Curie point has decreased from 200C to C with an increase inthe amount of Sn-substitution.

An inspection of samples No. 5 and No. 6 indicates that the simultaneousGeand Sn-substitution is effective for a further reduction in A H. Itwill be appreciated that the values of A H have become less than thosefor No. 3 and No. 4 samples, or less than one-fourth and one-tenth ofthat for the unsubstituted Ca-V garnet composition. The Curietemperature, however, has fallen to C or to 120C. To compensate for thelowering of Curie temperature with increasing Snor simultaneous SnandGe-substitution, a fraction of Ca ion on the 24c site is furtherreplaced with Y as seen in the No. 7 and No. 8 compositions. This hassucceeded in a further reduction in A H, for example, 32 (No. 7 sample)and 26 (No. 8 sample) and at the same time, raising the Curietemperature, for example, 222C (No. 7 sample) and 200C (No. 8 sample).In other words, the Curie temperature which has been lowered by Snorsimultaneous Snand Ge-substitution can be raised by the simultaneousY-substitution. Thus, Y- and Snor Y-, Snand Ge-substitution in the Ca-Vgarnet composition has succeeded in realizing low 41rMs, low A H, highCurie temperature, and improved temperature stability of 41rMs.

To evaluate the effect of Sn-substitution, several samples were preparedby varying x, with y fixed at 0.5 and 0.8 for z 0, and sintering at1260C for 10 hours and others by varying x, with y fixed at 1.2 and 1.5for z 0, and sintering at 1800C for 10 in the Ca-V garnet compositionsexpressed as FIG. 1 indicates the dependence of A H on x for thesesamples. The effectiveness of Sn-substitution for the improvement in A Hwill be readily appreciated from the fact that A H decreases rapidlywith increasing x in curves y 0.5, 0.8, 1.2, and 1.5.

For instance, A H exhibits an extraordinarily large value near x 0.167for y 0.5 by the abnormal phenomenon mentioned previously. But, A Hdecreases with increasing x beyond this value to reach A H 63 at x 0.5.In other words, A H has been improved to a value less than we of that atx 0. In similar manner, it takes an extraordinarily large value in thevicinity of x 0.067 for y 0.8, but decreases with increasing 1: beyondthis point to reach A H 60 at x 0.5. Thus A H has been improved to avalue of the order of /4 of that at x 0. The value A H 32 at x 0.5 for y=1.2 indicates an improvement of A H equivalent to 1/7 of that at x 0,while A H 14 at x 0.7 indicates an improvement equivalent to 1/12 ofthat at x 0. That A H can be improved by Sn-substitution under the Y-substitution will be readily evident from these curves in FIG. 1.

Referring to FIG. 3 which indicates dependence of 411-Ms on x it will beseen, in each case, that 4 rrMs increases with increasing x to reach amaximum at x 0.5 and then, decreases with increasing x. It can also benoted that the 490 Ms maximums at 0.5 become higher with increasingY-substitution, reaching the highest 41'rMs 1150 gauss for y 1.5. Thesecurves further demonstrate that 41rMs can be varied in a wide range, 200to 1250 gauss, by the Sn-substitution under the presence of Y and A H ismarkedly improved in the range of large 41rMs values.

In order to evaluate the effect of Sn-substitution in case z a: 0, thatis, under the coexistence of Y and Ge, the value of x was varied in therange 0 to 1.0 with z fixed at 0.3 and y at 1.4 in the formula mentionedabove. Saturation magnetization 41rMs and linewidth A H as a function ofx for these samples which were prepared by sintering at 1300C for hoursare shown in FIG. 5. The 4'ITMS curve (solid line) indicates that 47TMSincreases at first with increasing Sn-substitution to reach a maximum680 at x 0.5 and then, decreases with increasing x to become less than100 at x 1.0. The A H curve (dotted line) indicates that A H is 185 Oeat x 0, decreaseswith increasing x to reach A H 28 at x 0.3 and A H at x0.5 and then, increases steadily with increasing x.

The Sn-substitution under the coexistance of Ge and Y readily reveals amarked contribution to reduction in A H in the range in which 41rMsvalues are not so large, for instance, 680. This advantage isconsiderably offset, however, by the decreasing tendency of Curietemperature with increasing x as will be seen in FIG. 2 for z 0 and inTable 2 for z 0. It will be. noted in FIG. 2 that whereas the Curietemperature decreases with increasing x, it becomes higher withincreasing Y- substitution. For instance, the Curie temperature becomesless than 100C in the vicinity of x 0.6, 0.7, and 0.9 respectively for y0.5, 0.7, and 1.2, while it remains well over 100C even at x 1.0 for y1.5. Furthermore, the slopes of these curves become less steep withincreasing y. For instance, the Curie temperature decreases 125, 110,97, and 87 degrees Centigrade respectively with an increase in x from 0to 0.5 for y 0.5, 0.8, 1.2, and 1.5.

Although the Curie temperature rises with increasing y, but the resultsof extensive experimentation conducted by us has proven that the Ca-Vgarnet compositions, which exhibit Curie temperatures most suitable forpractical application, must have x and y values meeting the relation ofx 0.35y 0.3. The compositions which do not meet this relationship havebeen found to be difficult for reduction to practice in having low Curietemperature and large variations of 41rMs with temperature. Referring toFIG. 4, the hatched area indicates the effective range of the values ofx and y, where z 0, in the garnet compositions expressed by the formulamentioned above. The area between the lines of 3x y 0.8 and 3x y 1.2 isexcluded, because the abnormal phenomenon of A H occurs there.

An inspection of Table 2 willreveal that the Curie temperature decreaseswith increasing x, or Snsubstitution, when z 5F 0, falling below 150Cfor x in excess of 0.5. Accordingly, the range of it suitable forpractical application should be x 0.5 when temperature variations of41rMs are taken into consideration.

To conclude, materials suitable for practical use with loww A H, high41-rMs (1250 gauss at maximum), satisfactory Curie temperatures can bemanufactured within the range of 1: meeting the relationship x 5 0.35y0.3 for z 0 or within the range ofx meeting the relationship 0 x 0.5 forz 0.

The evaluate the effectiveness of Y-substitution, several samples with x0.3, 0.5, and 0.7 for z 0 were Referring to each curve in FIG. 6, itwill be noted that A H decreases with increasing y until it reaches aminimum and then, increases with increasing y. For instance, A H reachesa minimum 30 at y 1.5 for x 0.3, a minimum 20 at y 1.5 for 0.5, aminimum 14 at y 1.5 for x 0.7. The values of these minimums decreasewith increasing Sn-substitution and beyond these points, all increase inA H steadily to reach values approximately equal to or larger than thoseat y 0 such as A H=340 aty=2.7 forx=0.3, AH =3l8 at y 2.5 for x 0.5, A H280 at 2.3 for x 0.7, provided A H corresponds to y which meets theequation 1.5 0.5x 0.5y =0 (i.e. no vanadium in the composition).

A rapid increase in A H for y 2.4 is attributed to the insufficiency ofthe prescribed sintering temperature of 1300C for the maturity ofsintering with increasing Y. In view of this fact, 1: and y values aredefined as 0 y 2.5; 1.5 0.5x 0.5y 0 in order to lower A H. Thedegradation of the sintering property with increasing Y will also beevident from the experimental data (2 =t= 0) set forth in Table 3, inwhich A H becomes a minimum A H 20 at y 1.4 (sample No. 5) and thenincreases the Y-substitution.

Referring to FIG. 7 which shows the effect of Y- substitution on Curietemperature, there isa tendency toward a gradual increase in the Curietemperature with increasing Y, demonstrating the possibility ofcompensating for the lowering of Curie temperature with increasing Sncontent by Y-substitution. FIG. 7 also indicates a tendency toward thelowering of Curie temperature for 1.5 0.5x 0.5y 0 that is, when vanadiumcontent is nil.

This tendency is notably conspicuous for the data for z 0 contained inTable 3. For instance, the Curie temperature for sample No. 1 (Y 011 isless than 50C, but it increases with increasing Y-substitution to reach200C at y 2.0 (sample No. 6). However, it decreases thereafter withincreasing Y to reach a low value for sample No. 7 for which 1.5 0.5x0.5y 0.5z 0.

The Y-substitution is effective for lowering AH and at the same time,elevating the Curie temperature. But, with an increase inY-concentration, there arises the need for elevating the sinteringtmperature to bring sintering to maturity. For these reasons, theeffective x and y ranges are defined as follows: 0 y 2.5 and 1.5 0.5x0.5y 0 for z 0; or 1.0 y 2.4 and 1.5 0.5x 0.5y 0.52 0 for z 0.

To evaluate the effect of Ge under the coexistence of Sn and Y, severalsamples of different compositions with z from 0 to 0.8, x= 0.3 and y 1.4in the composition 3u u)( 2-1 z) 1.5+0.5.r+0.59-0.5: z 1- ,c ,,a ,)Owere prepared by sintering at 1300C for 10 hours.

FIG. 8 shows the results of measurement for these samples, indicatingboth 41rMs and A H as a function of z. Data on Curie temperatures forthese samples are shown in Table 4.

Referring to FIG. 8, it is noted that tn-Ms decreases with increasing Gesubstitution. For instance, values of 4'rrMs are 880, 530, and 200respectively at z 0, 0.3,

and 0.8. The value of A H, however, decreases from 50 Oe at z 'withincreasing z to reach a minimum 24 at z 0.5. As this point is passed, AH gradually increases with increasing Ge-substitution.

The tendency toward a decrease in both 4'rrMs and A H by Ge-substitutionunder the coexistence of Sn and Y is clearly observed from these curves.Data of Table 4 indicate a steady decrease in Curie temperature withincreasing Ge-substitution (z).

As z exceeds 0.5, the Curie temperature falls and the temperaturevariation of 41rMs becomes large. Therefore, an optimum 1 range for lowA H and small temperature variation of 4'n'Ms can be defined as 0 2 0.5.Therefore, materials suitable for practical use with low A H, such asless than 50 within 0 z 2 0.5 for x 0.3 and y 1.4, and optimum 41rMsvalues ranging be- Al-substituted yttrium iron garnet Y Fe Al O (curve0) were prepared. All of these samples had roomtemperature 411-Ms valuesof the order of 500 gauss. FIG. 9 shows variation of 41rMs withtemperature for these three samples.

A comparison of these curves a, b, and c readily reveals that thevariation of 41rMs with temperature for the two samples according to theproposed composition is less, at or near room temperature, than that forthe sample of the Al-substituted yttrium iron garnet. The values of A Hfor the sample corresponding to curve a and the Al-substituted yttriumiron garnet corresponding to curve 0 were in the range 40 to 60 Oe,while the value of A H for the sample corresponding to curve b was 26Oe.

tween 880 and 380 gauss can be manufactured. Table 1 To evaluate how theproposed Ca-V garnet composi- Sintertions contribute to the improvementin A H, several g g cmpsmon Te 2: samples with x 0.3 and 0.5, y from 1.2to 1.8, and z (gauss) (0e) (C) 0 were prepared by sintering between1300C and (Ca )(Fe )(Fe v 1350C for 10 hours. Table 5 lists values of41rMs, A H, z 1210 520 370 210 and Curie temperature for these samples.)(Fe )(Fe Table 5 indicates that A H has been reduced to 10 Oe l b 1210785 0 197 or less, demonstrating that these materials are emi- 3. nentlysuitable for use in low-loss devices for micro- 1210 400 98 200 waveapplications. The value A H 2.5 for sample No. 4. 6 was attained by useof No. 4 sample after careful pol- 210 276 190 135 lshrng for verygentle sphere shaping. Low values of A (C )(F S H of this order werealso achieved with other sam les, n m "0.1 Nos. 1, 2, 3, and 5, byobserving the same polisliing 1210 550 90 technique. The known Y- andln-substituted Ca-V garaX m mnets had A H of the order of 2.0 Oe, Curietemperatures (FeMGCMVLQOZ 390 120 as low as 140C, and high 41rMs inexcess of 1400 35 Ega, ,g,

auss. Generall s eakin the lower the value of mMs, the more difficultitiecomes to reduce A H. The 3, 1300 960 32 222 substituted Ca-V garnetcompositions contemplated by g g F this invention can claim to besuperior, in practical apf filfl'ffi f" 1300 530 26 200 plication to theknown Y- and ln-substituted Ca-V garnets in'that Curie temperatures areas high as 160C 40 TABLE 2 and 41rMs values are less than about 1200gauss. Curie Tempemure To demonstrate the effect of the proposed Ca-Vgara {4 a 3 (5% nets for improving the sintering properties, several 01220 samples according to the invention and a sample of the 0.3 1.4 0.3200 conventional yttrium iron garnet composition (sample 45 g: {'2 8';No. l) were prepared by sintering at various tempera- 1:0 1:4 0:3 70tures for 10 hours and their theoretical densities (sin- TABLE 3 teringdensity/X-ray density) X 100 and A H values were measured, as listed inTable 6. Sintcr- Table 6 indicates that the Ca-V garnets according to igs: this invention maintain excellent theoretical densities c (Gauss)(0e) ((3) in excess of 97 percent, whereas the theoretical density (Ca)(Fe Sn of the yttrium iron garnet is only 91.4 percent. In other f' b1210 120 50 words, to raise this value to the order of 97 percent, sin-55 (Ca Y tering at higher temperatures, 1450C or higher for in- ,f:stance, would be necessary, as has been known among 1Ge.a 1210 100 70those skilled in the art. Data contained in this table ;:S demonstratethat the Ca-V garnet materials according Ge.,' ,V,, ;)O,, 1250 320 35100 to this invention can be manufactured at sintering tem- 60 (canyiperatures lower than 1450C by more than Centie, n,; 1250 no 30 25 r d 10.: on ll To demonstrate the feasibility of manufacture of y y Ca-Varnets with low 41-rMs and small temperature l.l 0.l)( 2.- variatit m of41rMs, two samples of the composition ac- 65 730 20 cording to thisinvention, (Ca Y XFe Snm) l.n !.0)' 2.! 0.5 0.5) l2 (curve and(Fel'bsno'axFeh 1300 990 4 200 2.0 1.0)( 1.7 0.3)( 2.l5 0.85) 12 (curveand an o.|| 2.2)' 1.5 0.5)( 2.- 8 ,Ge lo 1300 1150 100 110 1.7 0.3)( 2.70.z o.os) 1z 1300 1280 125 r 229 TABLE 4 I y z Curie Temperature C) 0.31.4 0 230 0.3 1.4 0.1 220 0.3 1.4 0.3 200 t 0.3 1.4 0.5 168 0.3 1.4 0.8125 TABLE Sinter- Sample ing 4'nMs AH Curie No. x y z Temp. Temp. ('C)(Gauss) (0e) (C) 1 0.3 1.2 0 1300 700 10.5 195 2 0.3 1.6 0 1330 103010.0 206 3 0.3 1.8 0 1330 1140 10.7 210 4 0.5 1.6 0 1330 1120 9 160 50.5 1.8 0 1350 1230 8 167 6 0.5 1.6 0 1350 1120 2.5 160 TABLE 6 Sinter-Theore- Sample Composition ing tical AH No. Temp. Density(Y,)(Fe,)(Fe,)O 1300 91.4 170 1.6 lA)( l.7 0.3)( 2.- ,Ge n 1300 99.0 28

H HX 1.1 u.=)( 2.- 4 1 o.. o..) .1 1300 99.1 24

1.e i.4)( 1.s o.s)( 2.- 5 3 0..| 0.4) 12 1300 99.3 20

( Lo mX m omX L Q M mOH 1300 97.9 48

( u ulm gJX ze w 0 12 I300 1.8 l.2)( r 5 0.5) us u- What is claimedis: 1. Ferrimagnetic garnets having compositions expressed by theformula:

( 3u 2.1- z)( l.s+o.s+o.suy i.so.s.ro.su) 12 comprising; a. an amount ofSn expressed by x as follows:

0.3 5 .1: 0.5, b. an amount of Y expressed by y as follows:

1.2 y 2.0, and 0. wherein the values of x and. y which meet the relationof 0.8 3x+y 1.2 are excluded. 2. Ferrimagnetic garnets havingcompositions expressed by the formula:

: CERTIFICATE OF CORRECTION ii 3,7 3,045 October 2, 1973 r HideoTakamizawa et a1. Inventor(s) It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Column 10 line 12, the formula of claim 1 should read Ca Y Fe Sn Fe V 0j C '3 Y C 2-); X) C 1 5+0. 5+0. 5y 1. 5-0. SX-O. By 12 f.

Signed and sealed this 8th day of October 1974.

A Attest:

r MoCOY M. GIBSON JR. C. MARSHALL DANN Atjtesting Officer Commissionerof Patents USCOMM-DC 60376-969 FORM PO-1050(10-69) I U 5 GOVERNMENTPRINTING OFFICE

2. Ferrimagnetic garnets having compositions expressed by the formula:(Ca3 yYy)(Fe2 xSnx)(Fe1.5 0.5x 0.5y 0.5zGezV1.5 0.5x 0.5y 0.5z)O12comprising; a. an amount of Sn expressed by x as follows: 0.25 < or = x< or = 0.5, b. an amount of Y expressed by y as follows: 1.2 < or = y <or = 2.4, c. an amount of Ge expressed by z as follows: 0.2 < or = z <or = 0.4, d. wherein the values of x, y and z which meet the relation0.8 < or = 3x+y-z < or = 1.2 are excluded, e. and including thelimitation that 1.5- 0.5x-0.5y-0.5z>0.